The present invention is directed to seat track assemblies for motor vehicles, and more particularly to improvements in lock mechanisms for holding the seat track assembly in a fixed position.
Seat track assemblies have been used to move a seat, typically in at least forward and rearward directions in a motor vehicle. Such known seat track assemblies have a lower track assembly comprising a pair of spaced, parallel lower tracks and an upper track assembly comprising a pair of spaced, parallel upper tracks, with each upper track slidable over a corresponding lower track. A lock or latch mechanism is provided to secure the upper track with respect to the lower track. Such a latch can be, for example, a latch with windows mounted on one track which engage teeth on the other track, or a latch with a tooth mounted on one track which engages a slot in the other track. Typically a handle, often referred to as a towel bar, is used to operate the latch between a latching position and an unlatching position. It is desirable for such a lock or latch mechanism to provide continuous or positive engagement wherein if the towel bar is released, the latch automatically moves back to the latching position and the upper tracks are secured to the lower tracks.
One such example of positive engagement is found in U.S. Pat. No. 5,918,846 to Pascal Garrido, a co-inventor of the present invention. The latch of a seat track assembly is mounted on an upper track and is seen to have three locking pawls. Spring biased locking pawls are designed to engage slots in a lower track when the latch is in the latching position. The size of the pawls and slots and the relative position of each pawl with respect to the slots has been designed so that at least one of the pawls engages a slot (and thereby secures the upper track with respect to the lower track) no matter what the position of the upper track on the lower track.
There is a need for a seat track assembly having a latch capable on ensuring positive engagement between the upper and lower tracks and capable of withstanding the ever-increasing load requirements placed upon the seat. High loading on the seat tracks may be seen in all-belts-to-seat (xe2x80x9cABTSxe2x80x9d) applications, where seat belts and shoulder belts are attached directly to the seat instead of to the side and/or the floor of the motor vehicle.
In view of the foregoing, it is an object of the present invention to provide a seat track assembly which is of simple construction and low cost, and which has positive engagement of a locking device with the ability to endure high loading. It is an additional object of the present invention to provide a seat track assembly that is highly reliable in operation and which can be manufactured efficiently. Additional objects and optional features of the invention will be apparent form the following disclosure and detailed discussion of preferred embodiments.
In accordance with a first aspect, a seat track assembly comprises a lower track assembly having a lower track with a plurality of spaced slots, with each slot having a front wall and a rear wall, an upper track assembly operably engaging the lower track assembly and comprising an upper track slidable over the lower track, and a latch movable from a latching position securing the upper track with respect to the lower track to an unlatching position where the upper track is free to slide over the lower track. The latch comprises a plurality of locking pawls mounted on the upper track, with each locking pawl having first and second teeth with each tooth having a front face and a rear face. In the latching position the first tooth of the first locking pawl is received within a first slot and the second tooth of the first locking pawl is received within a second slot. An actuation fork mounted on the upper track guides the plurality of pawls into and out of engagement with the lower tracks.
In accordance with another aspect, the slots on the lower track are spaced apart by a slot distance and the first tooth of each pawl is spaced apart from the second tooth of the corresponding pawl by a tooth distance generally equivalent to the slot distance.
In accordance with another aspect, the slots on the lower track have a slot width, and each pawl has a pawl width which is generally twice the slot width.
From the foregoing disclosure and the following more detailed description of various preferred embodiments, it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology and art of seat track assemblies. Particularly significant in this regard is the potential the invention affords for providing positive locking between the upper track and the lower track of a motor vehicle and satisfying high strength requirements. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.